Kinetic and Thermodynamic Analysis of Pyrolysis of Agricultural Biomass Blends for Energy Recovery in North West Nigeria

North West Nigeria generates substantial quantities of agricultural biomass residues including groundnut shells, cotton stalks, and millet chaff that remain energy-underutilised, while persistent electricity deficits limit rural economic development. This study investigates the pyrolysis kinetics and thermodynamics of biomass blends comprising groundnut shell and cotton stalk in ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 from farms in Katsina State, focusing on their energy recovery potential. Thermogravimetric analysis was performed at heating rates of 5, 10, 20, and 40 degrees Celsius per minute from ambient to 900 degrees Celsius under nitrogen atmosphere. Kinetic triplets were determined using Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa model-free isoconversional methods. Thermodynamic parameters including enthalpy, Gibbs free energy, and entropy of activation were calculated from kinetic parameters. Activation energies for pure groundnut shell ranged from 142 to 218 kJ/mol across conversion fractions, while cotton stalk showed 128 to 197 kJ/mol. Blended samples exhibited positive synergistic interactions in the 200 to 450 degrees Celsius devolatilisation zone, with reduced activation energy at the 50:50 ratio, suggesting improved reactivity. The 50:50 blend also produced the highest volatile matter yield and most favourable enthalpy values, indicative of energy-efficient pyrolysis. Proximate and ultimate analysis of resulting biochars confirmed their suitability as solid fuel co-firing material. The study provides fundamental thermochemical data for biomass co-pyrolysis reactor design in North West Nigeria. Keywords: pyrolysis kinetics, biomass blends, thermogravimetric analysis, isoconversional methods, Katsina State